The effect of growth temperature on the irreversibility line of MPMG YBCO bulk with Y2O3 layer

This study was supported by the Turkish Scientific and Research Council (TUBITAK) research grant (TBAG-107T751) and Karadeniz Technical University - Turkey research grant (BAP 2008.111.001.8).In this study, three kinds of YBCO samples which are named Y1040, Y1050 and Y1060 were fabricated by Melt-Powder-Melt-Growth (MPMG) method without a seed crystal. Samples seem to be single crystal. The compacted powders were located on a crucible with a buffer layer of Y2O3 to avoid liquid to spread on the furnace plate and also to support crystal growth. YBCO samples were investigated by magnetoresistivity (rho-T) and magnetization (M-T) measurements in dc magnetic fields (parallel to c-axis) up to 5 T. Irreversibility fields (Him) and upper critical fields (11,2) were obtained using 10% and 90% criteria of the normal state resistivity value from rho-T curves. M-T measurements were carried out using the zero field cooling (ZFC) and field cooling (FC) processes to get irreversible temperature (T-irr). Fitting of the irreversibility line results to giant flux creep and vortex glass models were discussed. The results were found to be consistent with the results of the samples fabricated using a seed crystal. At the fabrication of MPMG YBCO, optimized temperature for crystal growth was determined to be around 1050-1060 degrees C. (C) 2017 Elsevier Ltd. All rights reserved